(a) Technical Field
The present invention relates to a dye-sensitized solar cell including a collector. More particularly, it relates to a dye-sensitized solar cell that can improve photo-electric conversion efficiency by maintaining an active area of a photo electrode to be as large as possible while using a collector for collecting a photo current.
(b) Background Art
As clean energy has recently begun to draw the attention of the automotive manufacturing world, photo-electric conversion devices such as solar cells have begun to be widely used. Among the solar cells, a silicon solar cell is already commercialized and applied as part of a sunroof installed in a vehicle. However, since the silicon solar cell has an opaque property and is expensive, its use is restricted.
Dye-sensitized solar cells that are spotlighted as translucent and transparent solar cells have been recently commercialized for various applications such as building integrated photovoltaic (BIPV), etc. Generally, as shown in FIG. 1, the dye-sensitized solar cell includes a working electrode and a counter electrode that are joined together. The working electrode includes a transparent conductive substrate on which a photo electrode (or a thick layer of an oxide semiconductor) such as TiO2 in which a Ru-based dye that can absorb light is absorbed is coated. The counter electrode is coated with a catalytic electrode using Pt. I−/I3−-based electrolyte is filled in a space between the working and counter electrodes.
The dye-sensitized solar cell is advantageous in that its manufacturing cost is relatively low, a transparent electrode can be manufactured, and it can be formed in a variety of different designs. Therefore, much research for the dye-sensitized solar cells has been performed. Particularly, research for applying the BIPV to the roof or windows of a building has been attempted. In addition, research for replacing the silicon solar cell that is currently applied to the roof of the vehicle with the dye-sensitized solar cell have been also attempted.
In order to apply the dye-sensitized solar cell to a large-sized application, a collector for collecting a photocurrent should be used. Referring to FIGS. 1 and 2, a working electrode 1 of a dye-sensitized solar cell includes a transparent conductive substrate 2, TiO2 photo electrodes 3 coated on the transparent conductive substrate 2, and collector cells 4 formed of a silver-based material and surrounded by a passivation layer 6. The collector cells 4 are arranged in lines and integrally connected with each other by a collector bottom portion 5 that is coated along a side edge of the transparent conductive substrate 2.
In addition, a counter electrode 7 includes a transparent conductive substrate, catalytic electrodes coated on the transparent conductive substrate, and collector cells that are thin and surrounded by a passivation layer. The collector cells extend to a collector bottom portion coated along a side edge of the transparent conductive substrate, thereby being integrally interconnected. A fill factor and a photocurrent value for the large-sized dye-sensitized solar cell are increased by using the collector. However, as the number of the collectors is increased, the active area of the photo electrode is reduced. Therefore, overall efficiency with respect to an aperture area is reduced.
In more detail, for the dye-sensitized solar cell modules having the same size, the areas of the photo electrodes may be different from each other by up to 50% in accordance with the structure of the collectors. As the area of the photo electrode is reduced, the photo current is reduced and thus the photo-electric conversion efficiency is reduced.
FIG. 3 is a view illustrating a photo current of the dye-sensitized solar cell in accordance with whether the collector is used. Table 1 shows the photo current and fill factor of the dye-sensitized solar cells in accordance with whether the collector is used. As shown in FIG. 3 and Table 1, it was noted, for the dye-sensitized solar cell using a working electrode that is formed by coating TiO2 on an entire surface of a transparent conductive substrate without using a collector, the fill factor is shown as a straight line of about 29.5% due to the increase of inner resistance. On the other hand, it was noted, for the dye-sensitized solar cell using a working electrode that is formed by forming a collector on the transparent conductive substrate, the fill factor is increased to 53%.
TABLE 1JscModuleVoc (V)(mA/cm2)FF (%)Efficiency (%)No collector0.621.9029.50.35(Ac: 68.89 cm2)Collector0.7612.67535.06(Ac: 87.88 cm2)4.45(Ap: 100 cm2)*Ac: Active Area AP: Aperture Area
Generally, when no collector is applied to the dye-sensitized solar cell, not only the fill factor but also the photo current is reduced. Therefore, it can be noted that, in order to increase the photocurrent and fill factor of the dye-sensitized solar cell module, the design of the collector for effectively collecting the photoelectrons is important.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.